RAM Electronics's Description

A bag of DP-50 developer is mixed with 1 litter of 25°C water. The exposed
PCB is gently agitated in solution. The exposed areas of resist will dissolve
into the solution, leaving the green resist in areas that were not exposed to
UV light.
If the resist does not fully remove from the exposed areas, the UV received
was insufficient. Possible causes are: Insufficient exposure time; the UV
source is old and not producing enough UV; incorrect UV frequency (use
350~450µm UV source); the artwork is not UV transmissive.
When the DP-50 solution no longer develops the resist in a timely manner, it
can be neutralized for safer disposal using the Kinsten BV5 kit, converting the
developer to a gel for easy disposal.
This Pack can be used for 400cm2 PCB size area.